The present invention relates generally to nonimpact printers, and in particular to a liquid supply system for such printers in which the printer head reciprocates across the surface of a recording sheet during each line scan.
In nonimpact printers of the above type, the printer head moves at such a high speed that a pressure variation occurs when the head makes a reversal at each end of the line scan path due to the inertial force of the liquid which is supplied through flexible conduits connected to the head.
A nonimpact printer shown and described in Japanese Patent No. 54-10449 comprises a loop of flexible liquid supply conduit having first and second half sections. One end of each half section is connected together with one end of the other section to an ink source and the other end of each section is connected together with the other end of the other section to a nonimpact printer head. The pressure variation that occurs in each of the half section of the loop is opposite to the pressure variation in the other half, such pressure variations could be cancelled out each other.
However, due to the flow resistance which exists in the inner wall of the supply conduit and its curvature of the conduit, the movement of liquid still tends to be converted into pressure variations which are not satisfactorily eliminated by the cancelling effect. The problem becomes particularly severe when an ink jet printer head of the on-demand type as disclosed in U.S. Pat. No. 3,747,120 is employed. More specifically, the pressure variation needs to be suppressed to a level below 0.033 kilogram/centimeter sqaure. If this value is exceeded undesirable ink droplets are discharged in response to a pressure increase and the meniscus of the ink is broken in response to a pressure decrease generating undesirable bubbles in the liquid chamber.